One-way clutches that only transmit rotation motion in a specified direction are assembled in the rotation transmission portion of various kinds of mechanical devices such as a starter for an idling-stop vehicle, various kinds of auxiliary devices for an automobile such as an alternator and the like, an oil pump for a transmission, and the like. Moreover, as disclosed in Japanese Patent No. 3,657,330, a one-way clutch and a rolling bearing may be made into a unit by using common parts. An example of such a one-way clutch device will be explained with reference to FIG. 8 and FIG. 9. In this one-way clutch device, a one-way roller clutch 1, and a pair of cylindrical roller bearings 2a, 2b that are arranged so as to be adjacent to both sides in the axial direction of the roller clutch 1 are made into a unit by using a common inner ring 3.
The inner ring 3 is made using metal plate, and comprises a cylindrical section 4, and a pair of outward-facing rim sections 5a, 5b that are formed by bending both end sections in the axial direction of the cylindrical section 4 outward in the radial direction. A cam surface 6 is provided in the middle section in the axial direction of the outer-circumferential surface of the cylindrical section 4 as an inner-diameter-side engaging surface of the roller clutch 1, and a pair of cylindrical inner raceways 7a, 7b of a pair of cylindrical roller bearings 2a, 2b are provided on both end sections in the axial direction of the cylindrical section 4. Plural concave cam sections 8 called ramp sections are formed on the cam surface 6 so as to be uniformly spaced in the circumferential direction. The depth of each of these concave cam sections 8 becomes larger going in a direction toward one side in the circumferential direction. Moreover, of the pair of inner raceways 7a, 7b, the outer diameter of one of the inner raceways 7a located on one side in the axial direction (left side in FIG. 8 and FIG. 9) is equal to or greater than the diameter of the circumscribed circle of the cam surface 6. On the other hand, the outer diameter of the other inner raceway 7b located on the other side in the axial direction (right side in FIG. 8 and FIG. 9) is equal to or less than the diameter of the inscribed circle of the bottom of the groove of the concave cam sections 8. Therefore, of the edges on both ends in the axial direction of these concave cam sections 8, the edges on one end in the axial direction, which are the edges of the ends on one side in the axial direction of the concave cam sections 8, are covered by stepped surfaces 9 and are not open in the axial direction. On the other hand, the edges of the other ends in the axial direction, which are the edges of the ends on the other side in the axial direction of the concave cam sections 8, are open in the axial direction.
Plural rollers 10, which are engaging elements of the roller clutch 1, a clutch retainer 11, and plural springs (not illustrated in the figures) are arranged on the outer-diameter side of the cam surface 6. The rollers 10 are made using a metal. The rollers 10 are held by the clutch retainer 11, and in a held state, are arranged so that there is one roller 10 on the outer-diameter side of each concave cam section 8. On the other hand, the clutch retainer 11 is made using a synthetic resin and formed into a cylindrical shape. The clutch retainer 11 has: a pair of ring-shaped rim sections 12a, 12b that are separated from each other in the axial direction and arranged so as to be concentric with each other; plural column sections 13 that span between the rim sections 12a, 12b and are arranged so as to be uniformly spaced in the circumferential direction; and protrusions 14a, 14b that are provided at plural locations in the circumferential direction of the inner-circumferential surfaces of the rim sections 12a, 12b. Pockets 15 for holding the rollers 10 so as to be able to roll freely and so as to be able to move a little in the circumferential direction are formed in portions that are surrounded on four sides by the pair of rim sections 12a, 12b and column sections 13 that are adjacent in the circumferential direction. The clutch retainer 11 is prevented from rotating with respect to the inner ring 3 by the protrusions 14a, 14b engaging with the concave cam sections 8. The springs are provided between the column sections 13 and the rollers 10, and elastically press the rollers 10 in a direction in which the depth of the concave cam sections 8 becomes smaller going in the circumferential direction.
Plural cylindrical rollers 16a, 16b of the cylindrical roller bearings 2a, 2b, and cylindrical bearing retainers 17a, 17b that hold these rollers 16a, 16b so as to be able to roll freely are arranged on the outer-diameter side of the pair of inner raceways 7a, 7b. The cylindrical rollers 16a, 16b are made using a metal, and the bearing retainers 17a, 17b are made using a metal or a synthetic resin. Of the pair of outward-facing flange sections 5a, 5b of the inner ring 3, the outward-facing flange section 5a that is located on one side in the axial direction is formed before the other components are arranged around the cylindrical section 4, so has a thickness dimension that is equal to the portion of the cylindrical section 4 where one adjacent inner raceway 7a is provided. On the other hand, the other outward-facing flange section 5b that is located on the other side in the axial direction is formed after the other components (at least the clutch retainer 1 and bearing retainers 17a, 17b) are arranged around the cylindrical section 4, so the thickness is thinner than the portion of the cylindrical section 4 where the other adjacent inner raceway 7a is provided.
When using this kind of one-way clutch device, the inner ring 3 is fastened around the outside of an inner-diameter side member 18 such as a rotating shaft. Moreover, an outer-diameter side member 19 such as a housing, pulley and the like is assembled on the outer-diameter side of the rollers 10 and cylindrical rollers 16a, 16b. Of the outer-diameter-side member 19 or another member such as an outer ring that is fitted and fastened on the inside of the outer-diameter-side member 19, a cylindrical surface 20, which is an outer-diameter side engaging surface, is provided on the portion of the inner-circumferential surface that faces the rollers 10, and a cylindrical outer raceway 21 is provided in the portion that faces the cylindrical rollers 16a, 16b. The cylindrical roller bearings 2a, 2b support radial loads that act between the inner-diameter side member 18 and the outer-diameter-side member 19, and relative rotation between the inner-diameter-side member 18 and outer-diameter-side member 19 is possible. On the other hand, the roller clutch 1 is able to transmit rotational force between the inner-diameter-side member and outer-diameter-side member 19 only when the inner-diameter-side member and the outer-diameter-side member 19 relatively rotate in a specified direction.
In other words, when the inner-diameter-side member 18 and the outer-diameter-side member 19 relatively rotate in a specified direction, the rollers 10 become wedged in the cylindrical space between the cam surface 6 and cylindrical surface 20 in the portions where the depth of the concave cam sections 8 becomes small. As a result, a locked state occurs in which transmission of rotational force between the small-diameter-side member 18 and large-diameter-side member 19 is possible. On the other hand, when the inner-diameter-side member 18 and the outer-diameter-side member 19 relatively rotate in the opposite direction of the specified direction, the inner-diameter-side member 18 and the outer-diameter-side member 19 are set into an overrun state and rotational force cannot be transmitted between these members.
In the case of this kind of one-way clutch device, the edges on one end in the axial direction of the concave cam sections 8 are covered by step surfaces 9. Therefore, the step surfaces 9 and the protrusions 14a that are provided on the inner-circumferential surface of one end in the axial direction of the clutch retainer 11 (left end section in FIG. 8 and FIG. 9) engage in the axial direction. The engagement between the step surfaces 9 and the protrusions 14a restricts displacement to one side in the axial direction of the clutch retainer 11 with respect to the inner ring 3. Due to this restriction, the clutch retainer 11 is prevented from displacing a large amount to one side in the axial direction during operation in the overrun state, and the retainer 17a of one roller bearing 2a is prevented from becoming strongly sandwiched between the clutch retainer 11 and one outward-facing flange section 5a. 
On the other hand, there are no step surfaces on the edges of the other end in the axial direction of the concave cam sections 8 that the protrusions 14b that are provided on the inner-circumferential surface of the other end section in the axial direction of the clutch retainer 11 (right end sections in FIG. 8 and FIG. 9) are able to engage with. Therefore, it is not possible to restrict displacement to the other side in the axial direction of the clutch retainer 11 with respect to the inner ring 3 by using the protrusions 14b. Consequently, the clutch retainer 11 moves a large amount toward the other side in the axial direction, and there is a possibility that the bearing retainer 17b of the other roller bearing 2b will become strongly sandwiched between the clutch retainer 11 and the other outward-facing flange section 5b. When the bearing retainer 17b becomes strongly sandwiched, the bearing retainer 17b is not able to rotate with respect to the inner ring 3, and there is a possibility that the overrun state will not be able to be maintained. Furthermore, when assembling the one-way clutch device, there is a possibility that the clutch retainer 11 that is assembled on the outer-diameter side of the inner ring 3 in the stage before forming the other outward-facing flange section 5b will accidentally come out from the outer-diameter side of the inner ring 3 toward the other side in the axial direction. Therefore, the work of forming the other outward-facing flange section 5b must be performed while paying careful attention that the clutch retainer 11 does not come out, so this work becomes troublesome.